The invention relates to a halogen incandescent lamp comprising
a tubular tipless glass lamp vessel sealed in a vacuum-tight manner and having an axis, this lamp vessel having at each end a first and a second seal, respectively, through which one respective current supply conductor is passed;
a filament having an axis axially arranged in the lamp vessel;
first and second current supply conductors, which are connected to the filament and have a first and a second foil-shaped part, respectively, which is accommodated in a respective seal, and an external part which is connected thereto and projects outwards from the lamp vessel;
a halogen-containing gas in the lamp vessel,
the foil-shaped parts each having a width dimension transverse to the axis of the lamp vessel.
The invention further relates to a method of manufacturing such a lamp, in which
a filament is axially arranged in a glass tube having an axis through an open first end thereof, means being provided for holding the filament positioned in the axial direction of the tube;
the glass tube is heated at the area of the first foil-shaped part and a first seal is formed in the tube, in which seal the first foil-shaped part is accommodated;
the tube is filled with a halogen-containing gas,
the tube is sealed in a vacuum-tight manner by heating the tube at the area of the second foil-shaped part and forming a second seal in the tube axially spaced apart from the first seal, the second foil-shaped part being accommodated in said second seal.
Such a lamp and a method of manufacturing such a lamp are known from U.S. Pat. No. 3,759,601.
In the manufacture of the known lamp, the second current supply conductor has at its external part a transverse beam having a length greater than the inner diameter and smaller than the outer diameter at the open first end of the tube. The transverse beam must abut against the open first end of the tube when the filament has been entirely introduced into said tube in order to hold the filament positioned in the axial direction in the tube during the manufacture of the lamp. Since in general the tube has a fairly thin wall of about 1 mm thickness, the length of the beam must lie within very narrow limits. However, when the filament is introduced into the tube, the beam can readily occupy an oblique position with respect to the axis of the tube or can be not entirely centered with respect to the tube, as a result of which the beam slides into the tube. In order to center the beam, the external part of the second current supply conductor is in the form of a helically wound wire, onto which a wire is wound, which spirals out to the wall of the tube.
A disadvantage of the known lamp is that its manufacture requires a complicated auxiliary construction. It is also a disadvantage that the external part of the second current supply conductor must be thin in order that it can be wound helically, just like the filament. The part projecting from the lamp vessel in the finished lamp must therefore be shielded from the air in order to prevent it from being burned.
U.S. Pat. No. 4,623,817 discloses a halogen incandescent lamp, which also has a tubular lamp vessel provided with a seal at both ends. To the filament which is axially arranged therein, current is supplied through only one of the seals, however. The lamp is consequently suitable for use in a copying apparatus, in which the other seal is not readily accessible for connection to an electric supply source. Through the relevant seal, two current supply conductors are passed into the lamp vessel, these conductors each having in this seal a foil-shaped part. One of the current supply conductors is connected to the adjacent end of the filament, while the second current supply conductor extends, whilst being surrounded by an insulator, to the other seal. This other seal accommodates a comparatively wide metal foil, which is connected through a conductor to the adjacent end of the filament for mechanically fixing the same. Said conductor is also connected directly or through the metal foil to the second current supply conductor to constitute a current path through the lamp.